1. Field of the Invention
The present invention relates to a wheel support bearing assembly for use in an automotive vehicle or the like and including an electric generator that serves as a means for detecting the number of revolution for an anti-skid braking mechanism, and an anti-skid brake device using such wheel support bearing assembly.
2. Description of the Prior Art
An anti-skid brake device (ABS) is known as used for detecting the incipiency of a tire lock occurring on a low frictional road surface or at the time of a panic stricken braking so that braking can be relieved to secure a tire grip to thereby stabilize the steerability. A sensor for detecting the number of revolutions of wheel for detecting the incipiency of the tire being locked is provided in a wheel support bearing assembly. Generally a pulsar ring is provided at an end portion or the like of raceways in a bearing outside and a sensor portion is provided in face-to-face relation with the pulsar ring.
Also, as a wheel support bearing assembly having the sensor built therein, such a bearing assembly as shown in FIG. 49 has hitherto been suggested, which includes a sensor portion 57 incorporated in a bearing outer race 51 which serves as a stationary member. See, for example, the Japanese Laid-open Utility Model Publication No. 1-156464. This prior art bearing assembly includes an outer race 51 for securement to a vehicle body structure, an inner race 52 mounted on a shaft portion of a hub wheel 54, a plurality of rolling elements 53 interposed between the inner race 51 and the outer race 52, and a sealing member 60. The rotation sensor 55 is of a structure wherein the sensor portion 57 is inserted into a hole 58 defined in the outer race 51 so as to confront and align with the pulsar ring 56 provided in an outer peripheral surface of the inner race 52. The use of the sensor built in the bearing assembly is effective to reduce the size of the wheel support bearing assembly as compared with the arrangement in which the pulsar ring and the sensor portion are disposed at the end of the bearing outside.
The prior art wheel support bearing assembly having built therein the sensor for detecting the number of revolutions of the wheel is such that detection signals generated by the sensor and supply of an electric power to the sensor are interfaced with the vehicle body structure by means of a wiring. In the prior art shown in FIG. 49, signal interfacing and supply of the electric power are carried out by means of an electric line 59. As such, the prior art wheel support bearing assembly makes use of the electric wire for drawing a sensor output or the like, and this electric wire is exposed to the outside of the vehicle body structure at a location between the wheel support bearing assembly and the vehicle body structure. Because of this, the electric line is susceptible to breakage or the like by the effect of stones hitting and/or frozen snow within a tire housing. Also, in the case of a steering wheel, it is necessary for the electric wire to be twisted beforehand and often times a relatively large number of processing steps is required. The electric wire referred to above also requires sheathing thereof and, therefore, reduction in weight of an automotive vehicle tends to be hampered and, in view of the large number of steps of fixing the electric wire, a high cost tends to be incurred.
Also, although the conventional wheel support bearing assembly of the type in which the sensor is built therein as shown in FIG. 49 can be assembled relatively compact, servicing of the rotation sensor 55 requires dismantling of the outer and inner races 51 and 52 of the wheel support bearing assembly, resulting in a problem that the servicing cannot be performed efficiently. For this reason, once the rotation sensor 55 fails to operate, the wheel support bearing assembly as a whole would be required to replace with a new one. In addition, although the conventional wheel support bearing assembly shown in FIG. 49 is of the type wherein the rotation sensor is built therein, since a portion of the sensor portion 57 is exposed outside the bearing assembly, no sufficient reduction in size thereof is still achieved. Yet, the conventional wheel support bearing assembly shown in FIG. 49 has a problem in that sealing of a hole 58 defined in the outer race 51 for receiving the sensor portion 57 is difficult to achieve, making it difficult to prevent any ingress of foreign matter.
In order to alleviate the foregoing problems, it may be contemplated to install the electric generator, which generates an electric power by relative rotation of the inner and outer races, within an annular space delimited between the inner and outer races, in combination with a wireless transmitting means for transmitting wireless a signal outputted from the electric generator and indicative of the number of revolutions of the wheel.
However, cable connection between the stator coil of the built-in electric generator and the wireless transmitting means positioned outside the bearing assembly requires a complicated and time-consuming wiring job, posing a problem associated with increase of the number of assembling steps. Also, a complicated and time-consuming procedure would also be required to seal a hole for passage of the cable.
Also, in an anti-skid brake device, the use of a magnetic coupling may be contemplated for the wireless transmission discussed hereinabove. In other words, magnetic communication may be used with no field emissive antenna. Where a feeble radio wave is used, it may be contemplated to amplitude modulate a carrier wave of a low frequency of about 2 MHz with a signal generated from the sensor.
However, in the case where the carrier wave is amplitude modulated with the feeble radio wave, external electromagnetic disturbances may often enter a receiver as an amplitude signal.
Where the wireless transmitting and receiving means is operable relying on the magnetic coupling, there is a problem that it tends to be adversely affected by up and down bumping of the wheel although there is little influence brought about by peripheral equipments.
Also, it may be contemplated to form the rotation sensor with the electric generator and also to use it as an electric power source for the wireless transmitting means. In such case, however, the electric power generated by the electric generator tends to decrease when the number of revolutions of the wheel decrease as a result of a braking force applied to the wheel, failing to sufficiently drive a transmitting circuit of the wireless transmitting means.
An object of the present invention is to provide an improved wheel support bearing assembly having a capability of detecting the number of revolutions of a wheel, substantially free from wire breakage occurring outside a vehicle body, and capable of contributing to reduction in weight and cost of the automotive vehicle.
Another object of the present invention is to provide an improved anti-skid brake device wherein a detection signal indicative of the number of revolutions of the wheel can be transmitted and received wireless, and the possibility of wire breakage taking place outside the vehicle body is eliminated, and which is less sensitive to an influence brought about by noises and substantially free from an erroneous operation while allowing the automotive vehicle to be manufactured lightweight at a reduced cost.
A further object of the present invention is to provide an improved anti-skid brake device which is less sensitive to an influence brought about by peripheral equipments during wireless transmission and reception, and also to an influence which would be brought about by up and down bumping of the wheel.
According to one aspect of the present invention, there is provided a wheel support bearing assembly for rotatably supporting a wheel relative to an automotive body structure. This wheel support bearing assembly includes an outer member having an inner peripheral surface formed with plural rows of raceways; an inner member having raceways defined therein in face-to-face relation with the raceways in the outer member; and plural rows of rolling elements accommodated between the raceways in the outer and inner members. An electric generator for generating an electric power as one of the outer and inner members rotates relative to the other of the outer and inner members is uniquely provided in combination with a wireless transmitting means for transmitting wireless a signal indicative of a number of revolutions of the wheel that is outputted from the electric generator.
According to the structure, since the electric generator capable of generating an electric power as a relative rotation between the outer member and the inner member is employed, it is possible to detect the number of revolutions of the wheel by the utilization of an output of the electric generator as a signal indicative of the number of revolutions of the wheel. Also, since the use has been made of the wireless transmitting means for transmitting wireless the signal outputted from the electric generator, no electric wire for drawing the detection signal indicative of the number of revolutions of the wheel to a control unit is necessary. Since the electric generator is used as a sensor, no electric power supply wire for the supply of an electric power to the sensor is necessary. The electric power obtainable from the electric generator can be used also as an electric power for the wireless transmitting means. For these reasons, no electric wire is exposed to the outside of the vehicle body structure and there is no possibility of the wires being broken, thereby eliminating any complicated and time-consuming wiring job while contributing to reduction in weight and cost of the automotive vehicle.
The wireless transmitting means which can be employed in the practice of the present invention may not be always limited to a type utilizing radio waves, but may be of a type capable of transmitting by means of a magnetic coupling, infrared rays of light, ultrasonic waves or any other signal that can travel in the air.
According to a second aspect of the present invention, the present invention provides an anti-skid brake device provided with a wheel support bearing assembly of the structure herein provided in accordance with the first aspect of the present invention. In this anti-skid brake device, the electric generator includes a pulsar ring mounted on a rotary member of a wheel, and a sensor mounted on a wheel support member in face-to-face relation with the pulsar ring and wherein the transmitting means is installed on the wheel support member. The anti-skid brake device so structured is operable to control a braking force in response to a signal indicative of a number of revolutions of a wheel that has been detected. Specifically, this anti-skid brake device includes a control circuit installed on a vehicle body structure for controlling the braking force, and a wireless transmitting and receiving means including the transmitting means and a receiving means installed on the vehicle body structure for transmitting and receiving wireless a signal of the sensor. The transmitting means is capable of transmitting a feeble radio wave by frequency modulating a carrier wave with the signal of the sensor.
According to the above described structure of the anti-skid brake device, since the signal detected by the sensor and indicative of the number of revolutions of the wheel is transmitted wireless from the transmitting means in the wheel support member to the receiving means in the vehicle body structure, no electric wire for transmission of the sensor signal between the wheel support member and the vehicle body structure is exposed to the outside of the vehicle body structure. For this reason, there is no possibility of the electric wire being broken by stone hitting and/or frozen snow within the tire housing. Also, the use of any electric wire for transmission of the sensor signal between the wheel support member and the vehicle body structure can be dispensed with, thereby eliminating the need of a complicated and time-consuming wiring work while contributing to reduction in weight and cost of the automotive vehicle.
In addition, since the wireless transmitting means employed is of a type capable of transmitting the sensor signal by frequency modulating (FM) a carrier wave to provide a feeble radio wave, selection of the modulating method makes it difficult to be adversely affected by external electromagnetic disturbances.
Yet, according to a third aspect of the present invention, there is also provided an anti-skid brake device provided with a wheel support bearing assembly of the structure herein provided in accordance with the first aspect of the present invention. The electric generator employed in this anti-skid brake device includes a pulsar ring mounted on a rotary member of a wheel, and a sensor mounted on a wheel support member in face-to-face relation with the pulsar ring and wherein the transmitting means is installed on the wheel support member, said anti-skid brake device being operable to control a braking force in response to a signal indicative of a number of revolutions of a wheel that has been detected. This anti-skid brake device includes a control circuit installed on a vehicle body structure for controlling the braking force, and a wireless transmitting and receiving means including the transmitting means and a receiving means installed on the vehicle body structure for transmitting and receiving wireless a signal of the sensor, wherein the transmitting and receiving means is of a type capable of transmitting and receiving wireless by means of a magnetic coupling between the transmitting means and the receiving means. A transmitting coil of the transmitting means and a receiving coil of the receiving means are arranged such that respective centers of those coils lie at right angles to an axis of revolution of the wheel and horizontally.
Since the transmission system based on the magnetic coupling has a directivity, the influence brought about by peripheral equipments is minimal. For this reason, any possible erroneous operation resulting from external disturbances can be avoided.
In communication using magnetism, depending on the ratio between the diameter and the length of the transmitting coil and depending on the distance between the transmitting coil and the receiving coil, there is a case in which the transmitting coil and the receiving coil are to be arranged in parallel to each other or a case in which they are to be arranged in series with each other. Where the transmitting coil and the receiving coil are arranged on the wheel support member and the automotive body structure, respectively, the distance between these coils is too large and, therefore, the series arrangement is generally preferred. However, in such case, deviation would occur in axes of coil ends as a result of up and down bumping of the wheel, resulting in a considerable change in transmission efficiency.
For this reason, if the transmitting coil and the receiving coil are so arranged that these coils lie at right angle relative to the axis of revolution of the wheel and horizontally, change in magnetic field towards the receiving coil can be suppressed more than the series arrangement even though the wheel undergoes up and down bumping.
It is to be noted that in the case of the steering wheel, the reason that the receiving coil is arranged so as to be perpendicular to the axis of revolution of the wheel is relative to the axis of revolution in the case of a straight run in which the wheel is not tilted relative to the automotive body structure.